1. Field of the Invention
The present invention generally relates to integrated circuit manufacture, and more particularly to thin films and their production and their uses in conferring advantages upon the semiconductor devices being manufactured, especially in rapid thermal chemical vapor deposition (RTCVD) processes.
2. Background Description
Conventionally, various films have been produced for use in circuit manufacture (such as making transistors), in a variety of types of chemical vapor deposition (CVD) processes. Examples of the various CVD processes are low pressure chemical vapor deposition (LPCVD), plasma-enhanced chemical vapor deposition (PECVD), high density plasma chemical vapor deposition (HDPCVD), rapid thermal chemical vapor deposition (RTCVD), cyclic deposition (CLD), atomic layer deposition (ALD), and mixed deposition (MLD) (i.e., a mixture of CLD and ALD); etc. The respective deposition processes differ significantly from each other as to their conditions (temperature, pressure, flow, etc.), equipment, parameters (substrate, time, etc.) and other variables.
Across these different kinds of deposition processes, different film production methods and films have been disclosed.
As an example films produced in LPCVD processes, U.S. Pat. No. 5,874,368 (Feb. 23, 1999) discloses formation of silicon nitrides from bis-tertiary butyl amino silane (BTBAS), in an LPCVD furnace, with pressure in a range of 20 mTorr to 2 Torr and a temperature range of 500–800° C. Also see Laxman et al., “A low-temperature solution for silicon nitride deposition,” Solid State Technology, April 2000, 79, disclosing LPCVD at 550–600° C.
U.S. Pat. No. 6,046,494 (Apr. 4, 2000) discloses forming an insulating layer in a semiconductor device at a relatively low temperature and without plasma for lower negative bias temperature instability and reduced dopant segregation. Methods are described for how to make a silicon nitride liner in a LPCVD furnace. For making the nitride layer, a chlorinated silane gas is used.
Another deposition that takes place during LPCVD, in an LPCVD batch furnace, is that of U.S. Pat. No. 6,268,299 (Jul. 31, 2001) disclosing formation of silicon-rich silicon nitride films used for barrier application. The silicion nitride films are deposited using various silicon containing precursors, e.g., bis-tertiary butyl amino silane (BTBAS), HCD, SiH4, etc., and NH3. The silicon to nitrogen ratio is modulated by changing the flow ratio of the silicon-containing precursor and NH3.
U.S. Pat. No. 6,268,299 (Jul. 31, 2001) discloses a low temperature process for depositing barrier nitrides using SiH4, dichlorosilane (DCS), BTBAS, HCD and mixtures of these gases in an LPCVD process. The flow ratio of NH3 to the precursors was varied to give different Si:N ratios.
Japanese Patent 2003051452 (Feb. 21, 2003) discloses BTBAS nitride deposition by an LPCVD furnace. Film thickness accuracy is said to be improved by optimizing the cleaning process.
Another film produced using an LPCVD furnace is that of JP 2001230248A (Nov. 26, 2002), disclosing BTBAS nitride deposition using an LPCVD furnace.
LPCVD, of course, is but one known class of CVD processes. Other manufacturing processes include PECVD and HDPCVD processes.
As an example of films made during PECVD and HDPCVD processes, see, for example, U.S. Pat. App. 2002/0090835 A1 (Jul. 11, 2002), by some of the same inventors as the present invention, disclosing formation of nitride films by BTBAS and related compounds with plasma energy, to give carbon incorporation, with particular suitability for PECVD and HDPCVD processes.
Other deposition processes include CLD, ALD and MLD. As an example of films made by CLD, ALD and MLD processes, see, e.g., U.S. Pat. App. 2003/0059535 A1 (Mar. 27, 2003). Deposition by CLD, ALD and MLD is disclosed for silicon nitride and other materials, using a variety of precursors. The reactions are carried out in cold-wall reactors.
Another category of deposition is that of RTCVD. Some films have been produced in RTCVD processes. For example, U.S. Pat. No. 6,153,261 (Nov. 28, 2000) discloses deposition of silicon nitride and oxide using BTBAS in an RTCVD process. See also U.S. Pat. App. 2001/0000476 A1 (Apr. 26, 2001).
U.S. Pat. No. 6,455,389 (Sep. 24, 2002) discloses an RTCVD process in which is formed a space layer that is a silicon nitride. Silane or dichloride silane is reacted with ammonia to form silicon nitride. Huang et al. describe an RTCVD process generally as having the temperature of the chamber is about 650 to 700° C. and the pressure of the chamber is about 200 to 600 torr, with the proceeding time of the RTCVD deposition process being about 2 to 4 minutes.
Nitride films are used in many different applications. However, the question of satisfying a particular application is multi-variate and may be relatively complicated. Turning, for example, to semiconductor devices, many different properties are important for advantageous functioning of a particular device. There are many competing considerations for manufacturing a particular device. A variety of different manufacturing techniques have been suggested, of which the following are only some examples.
For example, on the one hand, high carbon incorporation may be desired. U.S. Pat. App. 2001/0034129 A1 (Oct. 25, 2001) discloses an etching process for layers with high carbon concentration. The deposition uses TEOS, BTBAS, CCl4, CO2, etc. Spacers may be formed by CVD using BTBAS and NH3.
U.S. Pat. App. 2002/0111039 (Aug. 15, 2002) discloses certain silicon oxynitride spacers with low dielectric constant formed by BTBAS and nitrogen containing gases, with stoichiometry and other properties controlled to give a varied wet etch rate. Carbon incorporation is taught, to improve dry etch rate resistance.
U.S. Pat. App. 2002/0127763 (Sep. 12, 2002) teaches formation of an L-shaped spacer by in-situ oxide-nitride-oxide deposition using BTBAS and O2 and NH3 by LPCVD. There is provided a low-cost alternative L-shaped spacer, said to be better for gap-fill for a subsequent dielectric film.
It may be desired during manufacture to protect a gate stack from corrosives, such as reactive ion etching (RIE), wet etch, etc., as in U.S. App. 2003/0068855 A1 (Apr. 10, 2003), disclosing deposition of a nucleation (seed) layer of nitride deposited on a gate stack, followed by a nitride layer deposited on the seed layer by BTBAS. The carbon of the BTBAS nitride is used to protect the gate stack from corrosives.
U.S. Pat. No. 6,586,814 discloses use of BTBAS nitride for STI formation, using the etch resistance property of BTBAS nitride to help erosion of STI fill.
U.S. Pat. App. 2003/0127697 A1 (Jul. 10, 2003) discloses that, to generate compression in the channel of a PFET, the active region of a plurality of transistors is divided for each gate electrode and a thin STI is formed between adjacent gate electrodes.
In the case of semiconductor transistors, another property which has received some discussion is that of stress. For example, U.S. Pat. App. 2002/0063292 A1, discloses certain wafer orientation to generate local stress in the channel, and generally mentions a high-tensile nitride dielectric, but without specifically disclosing what measured value is meant by high-tensile or what specific nitride is an example of a high-tensile nitride.
U.S. Pat. App. 2002/0179908 A1 (Dec. 5, 2002) teaches various ways of introducing impurities, and controls internal stress of wiring in a thin film transistor (TFT) by introducing impurities and annealing.
U.S. Pat. No. 6,573,172 (Jun. 3, 2003) discloses formation of PECVD nitride films with different stress levels, on PMOS and NMOS devices.
Of course, optimizing any one property (such as a stress-related property) for a semiconductor device still must be balanced with satisfying many other necessary properties and performance considerations.
Also by way of background, in circuit manufacture, there has been used an assembly such as that shown in FIG. 1, in which, during wafer fabrication, a nitride liner 1 (such as a nitride film) covers a device 2 having a device active layer 21. Different types of nitride film conventionally have been available for wafer fabrication, providing different types of stress. Novellus plasma enhanced chemical vapor deposition (PECVD), Applied PECVD, and Applied Materials rapid thermal chemical vapor deposition (RTCVD) tools can provide Tensile Nitride films, and the stress is usually up to +10 G dynes/cm2, with some examples according to conventional products being: Novellus, +2.5 G dynes/cm2; PECVD, +4.5 G dynes/cm2; RTCVD SiH4, +9.8 G dynes/cm2.
As another example of a nitride liner, see U.S. Pat. App. 2003/0040158 A1, in which are disclosed two separate liners with different stress to improve mobility. One liner is made by LPCVD and the other liner is made by PECVD.
However, the conventional films and methods for producing nitride liners and other films have not necessarily provided all of the characteristics that may be desirable for field effect transistors (FETs) and other applications. For example, conventionally, nitride films used as a nitride liner have not been able to provide as much stress as would be desirable while balancing other needed characteristics. Nor are there adequately simple, feasible production methodologies for making films and semiconductor devices (such as FETs) to have desired characteristics.